Archaeologists tend to focus on the effects of human agency and often do not consider the environmental effects of other fauna or other 'natural' factors producing environmental changes. This important monograph identifies in very clear terms the fallacy and dangers of such a wholly anthropocentric approach as well as producing much fascinating information about beavers which is important not just to archaeologists but natural historians and those concerned with long-term environmental sustainability. The approach is refreshingly interdisciplinary, it is, as the jacket says, 'part ecology, part archaeology, and part history' and achieves its objectives most successfully on each account. The style is lucid, archaeological context and chronology are explained in a way which will make it accessible to those with limited archaeological knowledge. It is extremely clearly written, beautifully illustrated and an excellent read.

The received wisdom that European beavers did not have the environmental impact of their north American counterparts is challenged. This is achieved by detailed fieldwork documenting the effects of beavers on rivers in Brittany, where they were reintroduced in the late 1960s and the Drome, a tributary of the Rhone in France, which was one of the small relict populations which survived persecution in the nineteenth century and from which beavers are now expanding across continental Europe. The documented effects of the French beavers include lodges, dams, ponds, burrows, dens, exit paths, bypass channels, canals, beaver gnawed wood, dead wood and locally raised water tables and their ecological effects. The observations are beautifully documented with carefully drawn maps and plans effectively complemented by colour photographs on the same figure, a highly effective device providing a clear representation of the evidence and its landscape context. It is a model of a contextual approach which could be applied in other areas of archaeological research.

Documentation of the effects of French beavers is followed by consideration of their role as a human resource, and evidence from Somerset which sparked off this most profitable research topic. There are nine chapters presenting the evidence for beavers in Britain from the Pleistocene to the Post-medieval. The multi-period approach brings out the contrasting nature of the record in different periods. Before the Neolithic the evidence is mainly from natural contexts, after that period principally from archaeological features. Anglo-Saxon evidence for beavers is particularly from grave goods, while in the medieval period place-name evidence is particularly important and there is also written and iconographic evidence. The latter present difficulties of interpretation often telling us more about the perception of beavers rather than their physical presence in an area. Medieval imagery of beavers is dominated by the totally erroneous belief that when pursued the animal bites off its own testicles and is thus presents a role model of the virtues of sexual abstinence. That may be one lesson which is less enthusiastically taken up by field archaeologists!

The general assumption has been that beavers became extinct in Britain around the Norman conquest, the account written by Gerald of Wales of their activities in the Teifi in AD 1188 being one of the latest occurrences. It is now clear that relict populations survived significantly later, beyond the medieval period and possibly to the later seventeenth century in North Wales and maybe even the later eighteenth century in Yorkshire.

Beavers are of particular significance to archaeologists because under certain circumstances their environmental effects may be as extensive as that of humans, creating problems disentangling the effects of beaver from those of people. The more open sub-climax conditions which beavers created are likely to have attracted both people and grazing animals and, as the wetlands they created filled with sediment, fertile beaver lawns formed. At Dorney, Buckinghamshire, there is much evidence of beaver activity on the Thames and the beaver altered environment close to the river seems to have become the focus of Neolithic activity. The French fieldwork showed that beaver dams make ideal crossing points through wetlands and in this way they might have exerted a significant influence on axes of communication over a wider area. A number of cases are outlined where structures contain the distinctive beaver gnawed wood as well, sometimes, as wood worked by the use of stone or metal tools. Such sites include Star Carr, Yorkshire; the Baker platform in the Somerset Levels; Flag Fen in the Fenland; and Eadarloch crannog in Scotland. Other structures, which archaeologists have investigated, may be entirely, or mainly, of beaver construction as at West Cotton Northamptonshire and Skipsea Withow, Yorkshire. The conclusion is that beavers may help to create suitable contexts for activity or concentrations of resources which represent affordances influencing the pattern of past human activity.

One of the aims of the study (p88) was to establish whether beavers have an effect which would be evident from pollen analysis. No pollen or other palaeoenvironmental analyses are reported from the present day French beaver territories and it would be useful to know why this source of enquiry was not followed up. Perhaps it is because the French beavers are within partially open agricultural landscapes which are likely to represent poor analogues for the conditions of prehistory. The effects of beavers on the vegetation were, however, observed and it is concluded that they generally diversified woodland composition rather than lead to the loss of woodland. The types of vegetation changes seen in the French field studies are not considered likely to have registered in pollen diagrams to the extent which may have led to their being confused with human activity. However, sites which have been colonised over more extended timescales, and in certain topographic contexts of wide, gently graded floodplains are likely to have produced larger scale effects. A series of dams could have flooded large areas leading to vegetation effects significantly greater than those observed in these case studies. Indeed an earlier study (Coles & Orme 1983) which considered beavers in the Canadian landscape suggested the effects on vegetation were in some areas extensive. Less emphasis is given to that here and the question is whether this is because more detailed field observation has led to a down scaling of the expected extent of beaver impacts or simply because the focus here is firmly on the impact of European beaver species in reaction to those who responded to the earlier paper with the argument that the environmental effects of European and North American Beavers differed. It is now evident that they produce a similar range of dams, other structures and environmental effects, although the British environment which they occupied will often have differed significantly from that created by deglaciation in parts of Canada. Some re-evaluation of the Canadian comparanda would have been useful here, but maybe that is something for a future paper.

Focusing on one species has the advantage that it enables the marshalling of a considerable body of new evidence and the evaluation of the full range of beaver contributions to environmental change and as human resources. The disadvantage of a single species approach here, and in natural history generally, is that it may somewhat mask the interactions between the target species and other environmental factors, including plant and animal species, which is the essence of an ecological approach. Beavers were not acting alone. They were one of a range of disturbance factors within Holocene woodland which included storms, floods, disease, grazing animals, wildfire and people, etc. Of these, grazing animals and people are identified here as the most potentially significant interactions with beavers, but the others will also have played a role. None of these factors is evenly distributed across the landscape, but will be more concentrated in particular places and particular periods of time. The effects of grazing animals will be concentrated in passes and migratory routes, along the margins of rivers lakes and in saltmarshes and swamp edges. The effects of storms are likely to be concentrated in particular topographic contexts especially susceptible to high winds and tree throw, and will be highly episodic. On the edges of open water another significant factor will be the effects of large concentrations of grazing birds creating a close cropped organic and nitrogen enriched sward of distinctive vegetation. The result of these combined factors and many others is a earlier Holocene environment which we may predict was a more complex vegetation mosaic than the unbroken tall canopied woodland which we often imagine. Vera (2000) has highlighted the important role of grazing animals in creating what he envisaged as a more park-like wildwood. However, he did not take account of the effect of other disturbance factors including beavers, wildfire and human agency. Human agency was even overlooked in the case of New England where the ethnohistorical record shows clearly that native American burning was a key factor in the park-like landscape recorded by the first European writers (Cronon 1983). Nor did Vera recognise that disturbance factors are spatially concentrated making it probable that there was a mosaic with tall canopied woodland in areas of low disturbance risk, park-woodland conditions where risk was higher and open conditions where high levels of grazing and other disturbance occurred.

It is concluded (p90) that at the beginning of the fourth millennium beavers may have had a greater influence on the British environment than people. This is a salutary thought given the number of pollen diagrams which have been interpreted as showing some evidence of human agency at about the time of the elm decline. Once again spatial distribution may be a factor. Reading this monograph I get the impression of particular concentrations of beaver activity in certain places: the river Kennet, parts of the Severn catchment, the Somerset Levels, the Fenland and Yorkshire where the effects of beavers may have been disproportionately great. They may for instance have been one of the factors creating areas of open water and a generally less tree covered landscape in the middle Kennet around Thatcham where there is a major concentration of early Mesolithic activity. Evidence of Mesolithic burning is now well documented from upland, lakeside, riverine and, in western Britain particularly in coastal wetland contexts (Bell 2007), and from research in the Kennet Valley. Thus, the jury may be out for sometime on the question of whether people, or beavers, were the more significant environmental disturbance factor before farming became widespread. A major achievement of this study is to show that in evaluating the environmental effects of past human communities we have also to consider interactions between people and other disturbance factors of which the best documented to date is beavers.

Perhaps the most important reason why this study will be so influential, and highly topical, is that active consideration is currently being given to beaver reintroduction to Britain. They are already present on four sites but are enclosed within fences. In future they may be allowed to colonize more widely. The case for this is extremely strong and very clearly presented in this monograph. The European Union Habitats Directive requires member states to consider reintroductions. Beavers would undoubtedly make a major contribution to nature conservation and biodiversity particularly the expansion of wetland habitats of great conservation importance. They are a keystone species, the introduction of which to an area creates conditions suitable for other species and thus increases biomass. A strong case can also be made that, where they create dams and wetlands, that increases water storage capacity and reduces flood hazard downstream. The carefully documented evidence presented here for their geomorphological and environmental effects and the fact that beavers were present in Britain until a few hundred years ago adds considerable weight to the case for introduction. It is the best possible example of what should be an important new mission for archaeologists in the twenty-first century: helping to document the past history of habitats worthy of conservation and thus contribute to the creation of more sustainable environments for the future.